diff --git a/.github/workflows/actionlint.yml b/.github/workflows/actionlint.yml
index cd625595f..492c9ae04 100644
--- a/.github/workflows/actionlint.yml
+++ b/.github/workflows/actionlint.yml
@@ -24,7 +24,7 @@ jobs:
     permissions:
       contents: read
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Run actionlint
         uses: rhysd/actionlint@v1.7.11
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index a5b13858d..8b6ceeeb9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -38,7 +38,7 @@ jobs:
     env:
       PYTHONPATH: src
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python ${{ matrix.python-version }}
         uses: actions/setup-python@v5
@@ -111,7 +111,7 @@ jobs:
       contents: read
       security-events: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v5
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index 8100b5704..ec0adfefc 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -36,7 +36,7 @@ jobs:
       matrix:
         language: ["python"]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       # Database must be initialized before dependency install (advanced setup).
       - name: Initialize CodeQL
diff --git a/.github/workflows/docs-audit.yml b/.github/workflows/docs-audit.yml
index dd9b32a91..6d8f94399 100644
--- a/.github/workflows/docs-audit.yml
+++ b/.github/workflows/docs-audit.yml
@@ -37,7 +37,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 10
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Set up Python
         uses: actions/setup-python@v5
diff --git a/.github/workflows/supply-chain-audit.yml b/.github/workflows/supply-chain-audit.yml
index 35f3d41ac..373ec1115 100644
--- a/.github/workflows/supply-chain-audit.yml
+++ b/.github/workflows/supply-chain-audit.yml
@@ -23,7 +23,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 30
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v5
@@ -56,7 +56,7 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v6
 
       - name: Install uv
         uses: astral-sh/setup-uv@v5